Method for anchoring and sealing a cannula assembly to the body of a patient

ABSTRACT

A cannula assembly for use in laproscopic surgery includes a cannula having a proximal end for use in orientating the assembly into an abdominal cavity, a distal end for insertion into a patient, and a passage through which surgical instruments can be inserted. An expandable feature in the form of an anchor is located toward the distal end of the cannula and is selectively expandable and collapsible. The feature in its expanded state prevents withdrawal of the cannula. A collar is pushed distally until it releasably cinches to the outside of the abdominal cavity thereby creating an airtight seal and stabilizing the assembly. The collar has a friction fit with the cannula designed to prevent excessive force against the cavity walls.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/881,830, filed Oct. 13, 2015; which is a divisional of U.S.application Ser. No. 14/195,395, filed Mar. 3, 2014 (now U.S. Pat. No.9,155,550); which is a continuation of U.S. application Ser. No.13/913,120, filed Jun. 7, 2013 (now abandoned); which is a continuationof U.S. application Ser. No. 12/802,032, filed May 28, 2010 (now U.S.Pat. No. 8,466,659); which is a continuation of U.S. application Ser.No. 11/430,431, filed May 9, 2006 (now abandoned); which is a divisionalof U.S. application Ser. No. 10/680,973, filed Oct. 7, 2003 (now U.S.Pat. No. 7,041,055); which claims the benefit of U.S. ProvisionalApplication No. 60/416,665, filed Oct. 7, 2002; U.S. ProvisionalApplication Nos. 60/424,752; 60/424,754; and 60/424,755, each filed Nov.8, 2002; U.S. provisional Application Nos. 60/425,506; 60/425,522; and60/425,523, each filed Nov. 12, 2002; and U.S. Provisional ApplicationNo. 60/439,759, filed Jan. 13, 2003; all of which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a stabilized cannula adapted to seal againstthe loss of gas pressure from a body cavity of a patient during asurgical procedure.

Description of the Prior Art

The insertion of a cannula into an abdominal cavity during laparoscopicsurgery is generally accomplished using one of two methods. In the firstmethod, a hollow needle is inserted into the body cavity prior to theinsertion of the cannula so that the cavity can be expanded with a gas,such as carbon dioxide. Thereafter, the cannula is inserted along with aremovable sharp obtruator. The obtruator blade cuts through theabdominal wall allowing the surrounding cannula to penetrate into theinterior of the cavity. The obtruator is then removed leaving an entryport for various laparoscopic tools to be inserted into the cavity. Thecannula is equipped with a seal at its proximal end to ensure that thecavity remains pressurized with the insertion and removal of variousinstruments. Pressure loss between the cannula and the cavity wall isreduced by the tightness of the fit between the cannula and the cavitywall because the outside diameter of the cannula is larger than theobtruator entry wound. Generally, the obtruator used in this method isequipped with a spring-activated shield that is designed to cover theblade as soon as the interior wall is penetrated to avoid inadvertentpuncturing of the organs present inside the cavity. These shieldssometimes fail to close quickly enough to avoid injuries, particularlyif an organ such as the bowel is attached to the cavity wall.

A known method that avoids injuries associated with the obtruator shieldinvolves direct incision of the wall by the surgeon. Using a smallscalpel, the surgeon makes an incision through the cavity wall into theabdominal cavity and inserts a finger into the cavity to feel for organsthat might be attached to, or near the abdominal wall. Upon adetermination that no organs are attached to the abdominal wall, acannula with an obtruator having a blunt tip is inserted through thecut. After placement of the cannula, the obtruator is removed. Thepurpose of the blunt tip of the obtruator is to guide the cannulathrough the cut down to wound.

Both of the above described methods of insertion are prone to gasleakage and the lack of a proximal-to-distal stability of the cannula.Various techniques have been attempted to minimize these problems. Knownanchors for use with laparoscopic cannula have employed threaded sleevesadapted to be secured to the cannula and screwed into a laparoscopicpuncture opening to secure the instrument in place. An anchor of thistype is found in U.S. Pat. No. 5,217,441. U.S. Pat. No. 5,002,557 toHasson discloses an inflatable balloon that seals the cannula againstthe inside wall of the cavity and stabilizes the cannula by employing atapered collar that cinches against the outside wall of the cavity, ineffect sandwiching the cavity wall between the collar and the inflatedballoon. The Hasson device provides a sufficient seal and adequatecannula stability, but is difficult to operate. The balloon must beinflated with an external hypodermic syringe or other means through astop cock. Additionally, sealing the cannula with the cavity wallinvolves three steps: inflating the balloon, pushing a tapered collarsnugly against the external surface of the cavity wall, and securing thecollar in place with a set screw. U.S. Pat. No. 5,697,946 to Hopper etal. discloses a balloon-anchoring device that does not require the useof a proximal collar, but instead relies on a portion of the inflatingsurface to come in contact with the entry wound, thereby wedging thecannula into position. The Hopper device also involves an externalinflation device such as a hypodermic syringe connected to the cannulaby a stop cock or check valve.

U.S. Pat. No. 5,330,497 to Freitas et al. describes an anchored cannulathat uses an expandable mushroom-shaped anchor that in one embodimentopens when the user turns a detented actuator. The anchor cinches-upagainst the peritoneum when a seal is forced distally. The Freitasdevice offers an improvement over threads, but still suffers fromseveral drawbacks. In particular, the Freitas device is unduly complexat least in that it requires multiple steps in order to expand theanchor and seal the external cavity wall. A multiplicity of steps duringa surgical procedure can lead to a serious inefficiency. Devices thatare simple to operate make the procedure more efficient and lead to lesserrors. Therefore what is needed is a simple, easy-to-use cannulaanchoring and sealing device and method for use in laparoscopic surgery.

SUMMARY OF THE INVENTION

In accordance with the purposes of the present invention, as embodiedand broadly described herein, a cannula assembly of this invention isprovided for permitting the insertion of instruments into a body cavity.The cannula assembly includes a proximal end, a distal end, and alongitudinal axis, an inner sleeve, an outer sleeve coaxial with theinner sleeve, and a collar. The outer sleeve is fixedly attached to theinner sleeve at the distal end of the cannula and has an exteriorsurface. The outer sleeve forms an anchor that is radially expandablefrom the longitudinal axis from a retracted position to an expandedposition to anchor the cannula assembly to the body of a patient. Thecollar has an internal surface adapted to form a friction fit with theexterior surface of the outer sleeve to permit the collar to move aportion of the outer sleeve relative to the inner sleeve and move theanchor from the retracted position to the expanded position when thecollar is moved toward the distal end of the cannula assembly. Thefriction fit between the collar and the outer sleeve is configured topermit the collar to move relative to the outer sleeve only toward thedistal end of the cannula assembly when the anchor is in the expandedposition.

In accordance with the purposes of another embodiment of the presentinvention, as embodied and broadly described herein, a method of thisinvention is provided for anchoring and sealing a cannula assembly tothe body of a patient. The method includes providing the cannulaassembly having a proximal end, a distal end, a radially expandableanchor proximate the distal end, and a longitudinally movable collar;inserting the cannula assembly to a depth sufficient to place the anchorin a retracted position within the patient; and expanding the anchor bymoving the collar toward the distal end of the cannula assembly.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a cannula assembly according to onepreferred embodiment of the present invention having an anchor in aretracted position;

FIG. 2 is a side elevation view of the cannula assembly of FIG. 1 withthe anchor deployed in the abdominal cavity in an expanded position anda collar distally applied against the exterior of the abdominal cavity;

FIG. 3 is a fragmentary cross-sectional side view of the cannulaassembly of FIG. 1 with the anchor shown in the retracted position; and

FIG. 4 is a fragmentary side elevation view of the cannula assembly ofFIG. 1 with the anchor shown in the expanded position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

FIGS. 1-4 show a trocar cannula assembly for use with the presentinvention generally referred to by the number 100. As shown in FIG. 1,cannula assembly 100 includes a cannula 102 having a distal end 104, aproximal end 106 opposite distal end 104 along a longitudinal axis L, aninner sleeve 108, and an outer sleeve 110 that is preferably coaxialwith inner sleeve 108; and a movable annular collar 112.

As shown in FIG. 3, inner sleeve 108 has an interior surface 114 forminga passage 116 through which one or more instruments may pass, and anexterior surface 118. Referring again to FIG. 1, inner sleeve 108 has aproximal portion 120 that preferably includes a valve and/or seal tomaintain pressure when the cannula is inserted into a pressurizedcavity.

As shown in FIGS. 1 and 3, outer sleeve 110 has an interior surface 122and an exterior surface 124. At least a portion of interior surface 122is preferably adapted for slidable engagement with exterior surface 118of inner sleeve 108. Outer sleeve 110 forms an anchor 126 preferablylocated toward distal end 104 of cannula 102. Anchor 126 providesstability to the cannula assembly when deployed within the abdominalcavity, as will be described in more detail below.

FIG. 3 shows anchor 126 preferably having a plurality of finger hinges128 that are each separated by a slit 130. When anchor 126 moves from aretracted position shown in FIG. 3 to an expanded position shown in FIG.4, fingers 128 radially expand away from longitudinal axis L of cannula102 to anchor the cannula assembly to the patient. In order to preventinternal tissue from becoming entangled within fingers 128, anchor 126preferably includes a flexible cover membrane 132. Cover 132 may beresilient to bias anchor 126 to the retracted position to permit easyinsertion of cannula 102 into the abdominal cavity.

Inner sleeve 108 and outer sleeve 110 are preferably joined at distalend 104 of cannula 102 by conventional bonding materials. It will beappreciated by those skilled in the art that other ways to join theinner and outer sleeves together, whether chemically (e.g., glue),physically (e.g., ultrasonically weld or heat application), ormechanically, may be used and are within the broad scope of the presentinvention.

FIG. 1 shows an annular collar 112 preferably surrounding at least aportion of exterior surface 124 of outer sleeve 110. Annular collar 112preferably has an internal surface that forms a friction fit withexterior surface 124 to sealingly engage the outer surface of the bodycavity when anchor 126 is inserted into the patient and deployed.Preferably, annular collar 112, outer sleeve 110, and inner sleeve 108are constructed such that the force of the friction fit between annularcollar 112 and outer sleeve 110 is greater than the friction forceacting between outer sleeve 110 and inner sleeve 108. This may beaccomplished, for example, by selecting a material and snugness of fitbetween annular collar 112 and exterior surface 124 of outer sleeve 110and the fit between internal sleeve 108 and outer sleeve 110. Thispermits inner sleeve 108 to move relative to outer sleeve 110 beforeannular collar 112 will move relative to outer sleeve 110. Theinteraction between inner sleeve 108, outer sleeve 110, and annularcollar 112 is described in more detail below. It will be appreciatedthat annular collar 112 may exist in a variety of shapes and sizes, andneed not completely surround outer sleeve 110 in order to function forits intended purpose.

Having described the physical components of one preferred embodiment ofthe present invention, a method for its operation will now be described.Returning now to FIG. 1, cannula assembly 100 is positioned proximatethe surgical site to be operated upon, such as the abdominal cavity,with annular collar 112 in its proximal-most position and anchor 126 inthe retracted position. An obtruator is placed through proximal portion120, into passage 116 of inner sleeve 108, and beyond distal end 104 ofcannula 102.

The distal-most end of the obtruator is generally blade-shaped andpunctures the abdominal cavity, allowing cannula 102 to be forced intothe defect. Cannula 102 is inserted into the puncture to a sufficientdepth so that anchor 126 is below the peritoneum of the abdominalcavity. The obtruator is then removed from cannula 102.

With cannula assembly 100 properly positioned and inserted into theabdominal cavity, anchor 126 is deployed. Holding proximal portion 120stationary, annular collar 112 is moved away from proximal portion 120toward distal end 104. Annular collar 112 is preferably tightly fittedaround external surface 124 of outer sleeve 110 to form a friction fitsuch that movement of annular collar 112 will cause a correspondingmovement of a movable portion 134 of outer sleeve 110, which includesanchor 126. As annular collar 112 moves in the distal direction, movableportion 134 of outer sleeve 110 runs against a stationary portion 136 ofouter sleeve 110, which is joined to inner sleeve 108 at distal end 104.Finger hinges 128 of anchor 126 radially expand away from longitudinalaxis L to deploy anchor 126 into an arc shape so that anchor 126 movesfrom the retracted position shown in FIG. 3 to the expanded positionshown in FIG. 4. As annular collar 112 and outer sleeve 110 continue tomove distally, anchor 126 becomes fully deployed.

Once anchor 126 becomes fully deployed, movable portion 134 of outersleeve 110 reaches its maximum longitudinal distance of travel andbecomes stationary. At this point, the force of the friction fit betweenannular collar 112 and outer sleeve 110 is overcome by the force beingapplied to move annular collar 112 toward distal end 104. Annular collar112 begins to move relative to outer sleeve 110 and cinches-up againstthe outer surface of the abdominal wall as shown in FIG. 2. Afterannular collar 112 is sufficiently pressed against the skin so that bothsides of the abdominal cavity are sealed between annular collar 112 andanchor 126, annular collar 112 and proximal portion 120 are released.

While released, annular collar 112 and anchor 126 maintain a compressionof the abdominal wall between them. Movement of annular collar away fromthe abdominal wall is retarded by the friction fit between annularcollar 112 and outer sleeve 110. Anchor 126, owing to the resiliency ofmembrane 132 and to the elasticity of fingers 128, supplies a force thattends to restore the position of outer sleeve 110 relative to innersleeve 108 to its original position. The surfaces and/or materials ofouter sleeve 110 and inner sleeve 108 are designed such that thefriction force between them counters the restoring force of anchor 126.Thus, after annular collar 112 is moved distally and anchor 126 isdeployed, the friction force between inner sleeve 108 and outer sleeve110 is larger than the restoring force being exerted from anchor 126such that the relative position of inner sleeve 108 and outer sleeve 110is maintained once cannula assembly 100 is released. A sufficient sealbetween anchor 126 and annular collar 112 is maintained in part becausethe force of the friction fit between annular collar 112 and outersleeve 110 is greater than the friction force acting between innersleeve 108 and outer sleeve 110, which in turn acts to overcome theforce biasing anchor 126 to the retracted position.

After the surgical procedure, cannula assembly 100 is removed from theabdominal cavity by moving annular collar 112 toward proximal end 106 ofcannula 102. Because the friction force of the friction fit betweenannular collar 112 and outer sleeve 110 is greater than the frictionforce between outer sleeve 110 and inner sleeve 108, outer sleeve 110and inner sleeve 108 move relative to each other with a proximalmovement of annular collar 112. Anchor 126 collapses to the retractedposition as shown in FIG. 3, thus permitting the withdrawal of cannulaassembly 100 from the patient.

To summarize, the user holds proximal portion 120 in one hand andannular collar 112 in the other hand and applies a force separating thetwo. This action moves portion 134 of outer sleeve 110 and inner sleeve108 relative to one another, and therefore deploys anchor 126. Asannular collar 112 and the movable portion of outer sleeve 110 continueto move toward distal end 104, anchor 126 becomes fully deployed.Thereafter, annular collar 112 begins to move relative to outer sleeve110 and cinches-up against the skin. The friction fit force betweenannular collar 112 and outer sleeve 110 is preferably sized such thatthe force needed to overcome the friction fit force to move annularcollar 112 relative to outer sleeve 110 is within the safe limits toprevent over insertion of cannula assembly 100 into the abdominalcavity.

Cannula assembly 100 may be used in surgeries other than laproscopicsurgery. Additionally, it will be appreciated that other forms ofanchors may be used with the cannula of the present invention and stillremain within the broad scope of the present invention.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A method for anchoring and sealing a cannulaassembly to the body of a patient, the method comprising the steps of:providing the cannula assembly having a proximal end, a distal end, anda longitudinal axis passing through the proximal and distal ends, thecannula assembly having an inner sleeve having an interior surfaceforming a passage through the cannula assembly and the inner sleevehaving an exterior surface, the cannula assembly having an outer sleevehaving an interior surface adapted for slidable engagement with theexterior surface of the inner sleeve, the inner sleeve and the outersleeve being joined to one another proximate the distal end of thecannula assembly, the outer sleeve having a radially expandable anchortoward the distal end of the cannula assembly, the radially expandableanchor being configured to be movable between a retracted position andan expanded position, and the cannula assembly having a longitudinallymovable collar having an internal surface forming a friction fit withthe exterior surface of the outer sleeve, a force sufficient to overcomethe friction fit being greater than a force to move the radiallyexpandable anchor from the retracted position to the expanded position,the longitudinally movable collar being configured for axial movementalong the longitudinal axis to expand the radially expandable anchor andseal an opening into the patient on an outside portion of the patient, afirst portion of the collar located in a plane extending along thelongitudinal axis, the first portion of the collar being movable from atleast a first position in the plane to a second position in the planevia the axial movement of the collar; inserting the cannula assembly toa depth to place the radially expandable anchor in a retracted positionwithin the patient; expanding the radially expandable anchor from theretracted position to the expanded position by moving the collar and theouter sleeve together toward the distal end of the cannula assembly,movement of the collar moving the first portion thereof from the firstposition to the second position, and movement of the collar and theouter sleeve as a unit providing the force to move the radiallyexpandable anchor from the retracted position to the expanded positionwithout overcoming the friction fit between the internal surface of thecollar and the exterior surface of the outer sleeve; and sliding thecollar toward the distal end of the cannula assembly after the expandingof the radially expandable anchor from the retracted position to theexpanded position with sufficient force to overcome the friction fit. 2.The method of claim 1, further comprising forming a seal against anexterior surface of a patient after the radially expandable anchor isexpanded.
 3. The method of claim 1, further comprising locking thecollar against an exterior surface of a patient after the radiallyexpandable anchor is expanded.
 4. The method of claim 1, furthercomprising moving the collar toward the proximal end of the cannulaassembly to retract the radially expandable anchor and remove thecannula assembly from the patient.
 5. The method of claim 1, wherein thesliding of the collar toward the distal end of the cannula assemblyafter the expanding of the radially expandable anchor from the retractedposition to the expanded position continues until contacting thepatient.
 6. The method of claim 5, further comprising sealing an openinginto the patient between the collar on an outside portion of the patientand the radially expandable anchor on an inside portion of the patient.7. The method of claim 1, further comprising holding the proximal end ofthe cannula assembly during the expanding of the radially expandableanchor.
 8. The method of claim 1, wherein both the expanding of theradially expandable anchor and the sliding of the collar toward thedistal end of the cannula assembly occurs in one continuous motion toexpand the radially expandable anchor and seal an opening into thepatient between the collar on an outside portion of the patient and theradially expandable anchor on an inside portion of the patient.
 9. Themethod of claim 1, wherein the plane is oriented vertically, and theplane divides the outer sleeve of the cannula into a first side portionand a second side portion.
 10. The method of claim 1, wherein the firstposition of the first portion of the collar is closer to the proximalend of the cannula assembly than the second position of the firstportion of the collar.
 11. A method for anchoring and sealing a cannulaassembly to the body of a patient, the method comprising the steps of:providing the cannula assembly having a proximal end, a distal end, anda longitudinal axis passing through the proximal and distal ends, thecannula assembly having an inner sleeve having an interior surfaceforming a passage through the cannula assembly and the inner sleevehaving an exterior surface, the cannula assembly having an outer sleevehaving an interior surface adapted for slidable engagement with theexterior surface of the inner sleeve, the inner sleeve and the outersleeve being joined to one another proximate the distal end of thecannula assembly, the outer sleeve having a radially expandable anchortoward the distal end of the cannula assembly, the radially expandableanchor being configured to be movable between a retracted position andan expanded position, and the cannula assembly having a longitudinallymovable collar having an internal surface forming a friction fit withthe exterior surface of the outer sleeve, a force sufficient to overcomethe friction fit being greater than a force to move the radiallyexpandable anchor from the retracted position to the expanded position,the longitudinally movable collar being configured for axial movementalong the longitudinal axis to expand the radially expandable anchor andseal an opening into the patient on an outside portion of the patient;inserting the cannula assembly to a depth to place the radiallyexpandable anchor in a retracted position within the patient; expandingthe radially expandable anchor from the retracted position to theexpanded position by moving the collar and the outer sleeve togethertoward the distal end of the cannula assembly, movement of the collarand the outer sleeve as a unit providing the force to move the radiallyexpandable anchor from the retracted position to the expanded positionwithout overcoming the friction fit between the internal surface of thecollar and the exterior surface of the outer sleeve; and sliding thecollar toward the distal end of the cannula assembly after the expandingof the radially expandable anchor from the retracted position to theexpanded position with sufficient force to overcome the friction fit,wherein the collar includes a first portion located in a plane, theplane extending through the longitudinal axis and dividing the outersleeve of the cannula into a first portion and a second portion, thefirst portion being movable from a first position in the plane to asecond position in the plane via the axial movement of the collar. 12.The method of claim 11, further comprising moving the collar toward theproximal end of the cannula assembly to retract the radially expandableanchor and remove the cannula assembly from the patient.
 13. The methodof claim 11, wherein the sliding of the collar toward the distal end ofthe cannula assembly after the expanding of the radially expandableanchor from the retracted position to the expanded position continuesuntil contacting the patient.
 14. The method of claim 11, wherein theplane is oriented vertically, and the first portion of the collar islocated at or adjacent one of an upper portion and a lower portion ofthe outer sleeve.
 15. The method of claim 11, wherein the first positionof the first portion of the collar is closer to the proximal end of thecannula assembly than the second position of the first portion of thecollar.
 16. A method for anchoring and sealing a cannula assembly to thebody of a patient, the method comprising the steps of: providing thecannula assembly having a proximal end, a distal end, and a longitudinalaxis passing through the proximal and distal ends, the cannula assemblyhaving an inner sleeve having an interior surface forming a passagethrough the cannula assembly and the inner sleeve having an exteriorsurface, the cannula assembly having an outer sleeve having an interiorsurface adapted for slidable engagement with the exterior surface of theinner sleeve, the inner sleeve and the outer sleeve being joined to oneanother proximate the distal end of the cannula assembly, the outersleeve having a radially expandable anchor toward the distal end of thecannula assembly, the radially expandable anchor being configured to bemovable between a retracted position and an expanded position, and thecannula assembly having a longitudinally movable collar having aninternal surface forming a friction fit with the exterior surface of theouter sleeve, a force sufficient to overcome the friction fit beinggreater than a force to move the radially expandable anchor from theretracted position to the expanded position, the longitudinally movablecollar being configured for axial movement along the longitudinal axisto expand the radially expandable anchor and seal an opening into thepatient on an outside portion of the patient, a first portion of thecollar located on one of an upper portion and a lower portion of thecollar, the first portion of the collar being movable via the axialmovement of the collar from a first position corresponding to a locationof an upper portion of a first plane perpendicular to the longitudinalaxis to a second position corresponding to a location of an upperportion of a second plane perpendicular to the longitudinal axis;inserting the cannula assembly to a depth to place the radiallyexpandable anchor in a retracted position within the patient; expandingthe radially expandable anchor from the retracted position to theexpanded position by moving the collar and the outer sleeve togethertoward the distal end of the cannula assembly, movement of the collarmoving the first portion thereof from the first position to the secondposition, and movement of the collar and the outer sleeve as a unitproviding the force to move the radially expandable anchor from theretracted position to the expanded position without overcoming thefriction fit between the internal surface of the collar and the exteriorsurface of the outer sleeve; and sliding the collar toward the distalend of the cannula assembly after the expanding of the radiallyexpandable anchor from the retracted position to the expanded positionwith sufficient force to overcome the friction fit.
 17. The method ofclaim 16, further comprising moving the collar toward the proximal endof the cannula assembly to retract the radially expandable anchor andremove the cannula assembly from the patient.
 18. The method of claim16, wherein the sliding of the collar toward the distal end of thecannula assembly after the expanding of the radially expandable anchorfrom the retracted position to the expanded position continues untilcontacting the patient.
 19. The method of claim 16, wherein a thirdplane extends through the longitudinal axis and is oriented vertically,the first portion of collar moves in the third plane during movementthereof from the first position to the second position.
 20. The methodof claim 16, wherein the first position of the first portion of thecollar is closer to the proximal end of the cannula assembly than thesecond position of the first portion of the collar.